Systematic Review: Importance of fibers for allergy prevention
and treatment
For the purposes of this review, we focused on studies published during
the last 5 years. In our search, we included observational
epidemiological studies and clinical trials/intervention studies with
application of dietary fiber and/or prebiotics to prevent or treat
allergic diseases. Search terms are given in supplement 1 . Based on
these, 542 papers (235 from Pubmed and 307 from EMBASE) were retrieved.
After removal of duplicates, 512 papers remained. Finally, after
abstract and full text screening, we identified 16 studies that involved
either dietary prebiotic (n=7) or fiber (n=9) intake and measured
allergy-relevant outcomes. Exposures, interventions, and outcomes were
deemed to be too heterogeneous with respect to prebiotic/fiber type and
assessment of the outcome to attempt to pool the data for meta-analysis,
so results are summarised as a narrative systematic review only.
Several guidelines and systematic reviews have previously examined the
role of both fiber and prebiotic supplementation with respect to allergy
outcomes. A 2015 review by Orel et al. concluded that “the strongest
evidence on beneficial effects of prebiotics in children exists in
relation to the fight against constipation, poor weight-gain in preterm
infants and prevention of eczema in atopic
children.”37 The World Allergy Organization (WAO)
GLAD-P document stated that prebiotics could be added to the diet of
not-exclusively breastfed infants, both at high and at low risk for
developing allergy, however not in exclusively breastfed infants. This
is a conditional recommendation with very low certainty of
evidence.38 The supporting GRADE analysis for this
document regarding the use of prebiotics given to infants stated there
is “a possible effect of prebiotic supplementation in infants on the
reduction in the risk of asthma or wheezing”, in that prebiotics might
reduce the risk of recurrent wheezing in infants, but this had a very
low level of certainty due to “risk of bias, indirectness of the
evidence, and imprecision due to low number of events of the estimated
effect”.39 The Philippine guidelines on dietary
primary prevention state that prebiotics are not recommended to prevent
allergic diseases (with a strong recommendation level due to low quality
evidence).40 A systematic review from the United
Kingdom on dietary recommendations for infants and pregnant or lactating
mothers also reports that there is no clear evidence that prebiotic
supplementation reduces eczema at age ≤ 4 years (RR 0.75; 95% CI
0.56±1.01; I2 = 57%) and no association at age 5 to
14 years.41 This was followed by a systematic review
from Skorka et al.42 who noted inconclusive effects of
prebiotic supplementation in infant formula in influencing the
development of allergic diseases, with only a possible (though
methodologically limited) single study noting supplementation of infant
formula with GOS/FOS may decrease “some allergic reactions” and
GOS/FOS/AOS supplementation may reduce the risk of eczema. Lastly, a
systematic review supporting the new EAACI food allergy prevention
guidelines noted little to no effect for the role of prebiotics, though
also stated that the evidence for this is very
limited.43